10M45 CCS, what am I doing wrong ?

[jj2]

install 10m45 with 46ohm resistor with give me about 40 ma on the plate(320V) of my sun 2a3.
but a I am getting is a cracking sound of music .
cathode is 720 ohm with 20uf solen cap.
without the ccs it plays fine.
what am I doing wrong ?
Thanks for any help.

[dsavitsk]

These chips have a tendancy to oscillate. See Tubelab.com for some ways to stop this.

[tubelab.com]

The 10M45 will oscillate causing a crackling sound, and sometimes dead chips. Put a 1 K ohm resistor in series with the gate lead as close to the chip as posible. This has fixed it in all of the cases that I have seen.

[jj2]

Originally posted by tubelab.com
The 10M45 will oscillate causing a crackling sound, and sometimes dead chips. Put a 1 K ohm resistor in series with the gate lead as close to the chip as posible. This has fixed it in all of the cases that I have seen.

thanks tubelab.com
Installed 1K resistor, still no go.
replace 46 ohms with var resistor in negative pin of 10m45.
adjust var resistor while measuring cathode current, at 57ma it stop going up, var resistor measure at 18.2 ohms.
music come out fine but not great.
questions:
1) do I have to remove cathode cap & resistor, or how do I find out what size resistor to use with CCS on the plate ?
2) Is 18.2 not way to low for 10m45? according to the IXYS chart for 60ma it should be 40 ohms.
Thanks for the help

[tubelab.com]

How did you install the 10M45? Where in this circuit did you put it?

[rdf]

Originally posted by jj2
2) Is 18.2 not way to low for 10m45? according to the IXYS chart for 60ma it should be 40 ohms.

My experience has been the resisitor vs. output current graph in the datasheet doesn't mean much. The correct value also seems to vary sample to sample. Just use whatever works. I solder a mini ten-turn to the pins and keep it there until the circuit is ready for final build, which in my case usually means they never come out.

[jj2]

Originally posted by tubelab.com
How did you install the 10M45? Where in this circuit did you put it?

Tubelab I install it at the plate of the 2A3 after the 2.5k tap of the output transformer.
thanks.
[IMG]C:\Documents and Settings\jj\Desktop\sun ccs.jpg[/IMG]

[tubelab.com]

You can't put a CCS here. A CCS has a very high impedance and will severely distort the signal if put in series with the signal path.

Try puting the CCS in place of the cathode resistor. Leave the capacitor in place. The cathode capacitor becomes more important now since it is the only low impedance path to ground.